Turbomachines, such as gas turbines for example, typically comprise several stages of rotating rotor blades as well as stationary guide vanes. The rotor blades rotate together with a rotor. The rotor blades as well as the guide vanes are enclosed by a stationary housing of the gas turbine. In order to increase the output power and/or the efficiency of the gas turbine, it is important to optimize all components and sub-systems thereof, including the so-called seal systems. In a gas turbine aircraft engine, it is especially problematic to maintain a minimal gap between the rotating rotor blades and the stationary housing of a high pressure compressor of the engine, and also between the stationary guide vanes and a rotating rotor shaft of the high pressure compressor. Namely, the greatest temperatures and temperature gradients arise in the high pressure compressors, which makes it more difficult to maintain the appropriate minimum clearance gap. This also arises because so-called cover bands, as they are used in turbines, are not provided for compressor rotor blades and compressor guide vanes.
Because the guide vanes and the rotor blades in the compressor are not provided with a cover band, the ends or tips of the rotating rotor blades are subjected to a direct frictional contact with the housing during the so-called grazing of the blade tips along or into the surface of the stationary housing. Similarly, the free ends or tips of the guide vanes are subjected to a direct frictional contact with the adjacent surface of the rotor shaft. Such a grazing of the blade tips with the adjacent stationary components is caused, in connection with the setting of a minimal radial gap, due to production tolerances. During operation of the turbomachine, due to the frictional contact of the blade tips, material is abraded and removed from the blade tips, which leads to the formation of an increased gap size around the entire circumference of the housing and the rotor.
In order to avoid the above described enlargement of the gap, it is known in the prior art to provide a blade tip armor coating or cladding on the blade tips. The conventionally known armor claddings can be formed of hard material particles or abrasive particles. However, such a blade tip armor cladding is also subject to wear during operation of the turbomachine, and can also be damaged in this regard.